Effect of Different Combinations of Plant Growth Regulators on in vitro Propagation of Yam (Dioscorea Species)

Seed tubers are expensive, bulky and the multiplication rate in the field is very low. Shortage of seed tubers for planting is one of the major constraints for yam production in Ethiopia. No information is available on micropropagation of Dioscorea spp. in Ethiopia. To overcome such problem, the current study was, initiated to optimize type and concentration of plant growth regulators for shoot multiplication and rooting. Shoot multiplication and rooting in vitro were carried out using a completely randomized design with five replications. For shoot multiplication, shoots initiated from nodal cuttings were treated with BAP in combination with NAA. For rooting, the micro-shoots were transferred to ½ MS media containing NAA and IBA. Data on number of shoots per explant, roots per shoot and related growth parameters were recorded and statistically analyzed. The results showed that MS media supplemented with 1.5 mg/l BAP + 0.15 mgl -1 NAA gave an average of 6.40 ± 0.28 shoots per explant with a mean shoot length of 2.0±0.11 cm. MS supplemented with BAP (1.0 mg l -l ) and NAA (0.15 mg l -l ) gave 5.40 ± 0.28 with a mean shoot length of 1.84 ± 0.20 cm. Plantlets grown on half strength MS media supplemented with 2.0 mg l -l NAA and 0.5 mg l -l IBA produced 5.7 ± 0.27 roots per plantlet and an average root length of 4.63±0.23 cm. Thus MS + 1.5 mgl -1 BAP + 0.15 mg l -l NAA and 1/2 MS +2.0 mg l -l NAA + 0.5 mgl -1 IBA is the best hormone combination for shoot multiplication and in vitro rooting respectively.